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CVE-2026-23537 – Unauthenticated Arbitrary File Write / Potential RCE – Feast Feature Server < 0….

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Summary

CVE-2026-23537 is a critical unauthenticated arbitrary file write vulnerability (CWE-862: Missing Authorization) in the Feast Feature Server’s /save-document REST API endpoint, affecting all versions prior to 0.59.0. With a CVSS v3.1 base score of 9.1 (Critical), the flaw is exploitable remotely over the network with no credentials and no user interaction required. Successful exploitation allows an attacker to write arbitrary JSON files to the server’s filesystem — bypassing intended path restrictions — which can lead to denial of service through disk exhaustion or potential remote code execution via overwrite of application configuration files or startup scripts.

Technical details

  • Root cause: The /save-document endpoint lacks proper authorization controls (CWE-862), permitting unauthenticated HTTP requests to write JSON files to the server filesystem. File-location restrictions intended to confine permitted write paths can be bypassed, enabling writes to arbitrary locations on the host.
  • Trigger conditions: A remote attacker sends a specially crafted HTTP request to the /save-document endpoint. No authentication, privileges, or user interaction are required (CVSS: AV:N/AC:L/PR:N/UI:N).
  • Attack vector: Network-accessible REST API. Feast Feature Server is built on FastAPI and typically deployed via Docker or Kubernetes, with its REST API reachable over the network by default on port 6566.
  • Impact: Arbitrary JSON file writes to the server filesystem, including overwrite of application configuration files or startup scripts. This can result in denial of service through disk exhaustion, unauthorized modification of system state, and — where configuration or startup files are overwritten — potential remote code execution. Integrity and availability impacts are both rated High; confidentiality is not directly impacted (CVSS C:N/I:H/A:H).

Affected software

  • Feast Feature Server — all versions prior to 0.59.0
  • Red Hat OpenShift AI (RHOAI) — container images embedding Feast Feature Server versions prior to the fix, as tracked in the Red Hat security advisory for this CVE

Severity

  • CVSS v3.1 base score: 9.1 (Critical)
  • Vector string: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H

Mitigation and recommended actions

  • Immediate action: Upgrade Feast Feature Server to version 0.59.0 or later, which resolves this vulnerability.
  • If immediate patching is not feasible: Restrict network access to the Feast Feature Server REST API (default port 6566) to trusted internal networks only using firewall rules, Kubernetes NetworkPolicy, or an API gateway with authentication enforcement. Removing direct internet exposure eliminates the primary external attack surface.
  • Red Hat OpenShift AI users: Apply the updated RHOAI container images that bundle the patched Feast Feature Server version, as referenced in the Red Hat security advisory for this CVE.

IONIX Status

The IONIX research team is tracking ongoing exploitation attempts and recommends immediate patching. Potentially affected assets are outlined in this post.

References

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